1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device. More particularly, the present invention relates to a semiconductor device having a ferroelectric capacitor and a method for manufacturing the semiconductor device.
2. Description of the Related Art
A Ferro-electric Random Access Memory (FeRAM) element using a ferroelectric capacitive element (ferroelectric capacitor) as a storage capacitive element is a non-volatile memory device having the following characteristics. That is, a high-speed operation is enabled, power consumption is low and, writing and readout durability is excellent.
In a manufacturing process of such a FeRAM element, a continuity test or a potential inversion test of the ferroelectric substance is generally performed to inspect the presence of abnormalities.
On the other hand, the ferroelectric capacitor has a property of easily deteriorating due to moisture or hydrogen (referred to as “moisture”) which penetrates from the outside.
Therefore, there is proposed a structure that a ferroelectric capacitor is covered with an aluminum oxide film to block moisture from reaching the ferroelectric capacitor in a formation step of the FeRAM element and after formation thereof (See, e.g., Japanese Unexamined Patent Publication No. 2005-268617).
In a continuity test or a potential inversion test of the ferroelectric capacitor in a manufacturing process of a FeRAM element, there is generally used an external connection electrode pad to which a metal wire or a metal bump is finally connected. Further, a predetermined probe is brought into contact with the electrode pad to perform a predetermined test such as the potential inversion test of the ferroelectric capacitor.
However, when a probe test is thus performed, mechanical injuries may occur in an electrode pad due to contact with a probe. Further, after the probe test, a metal wire is connected also to the electrode pad with injuries in the same manner as in an electrode pad with no injury.
FIG. 14 schematically shows a state where in a FeRAM element, a metal wire is connected to an electrode pad after a probe test.
In FIG. 14, a FeRAM element 200 has a structure that a ferroelectric capacitor 203 comprising a layered product including a lower electrode 203a, a ferroelectric film 203b and an upper electrode 203c is formed within an interlayer insulating film 202 formed over a semiconductor substrate 201.
An active element such as a transistor and passive element such as a capacitive element formed over the semiconductor substrate 201 as well as other wiring layers provided within the interlayer insulating film 202 are not shown in the figure.
The ferroelectric capacitor 203 is electrically connected to a transistor (not shown) formed using the semiconductor substrate 201 as well as electrically connected to an electrode pad 205 through a connection via 204 connected to the upper electrode 203c of the capacitor 203. The electrode pad 205 has a state of being partially exposed from an opening provided in a protective film 206 formed over the pad 205.
A probe test on the FeRAM element 200 is performed using such an electrode pad 205.
More specifically, a probe is brought into contact with the electrode pad 205 to inspect overall continuity as well as potential inversion of the ferroelectric capacitor 203. In such a probe test, since the probe is brought into contact with the electrode pad 205, a concave portion 207a and/or a convex portion 207b are formed on the pad 205 as shown in the figure.
Further, after the probe test, a metal wire 208 for connecting to an external substrate is connected to the electrode pad 205.
However, when the concave portion 207a and/or the convex portion 207b are formed on the electrode pad 205, the concave portion 207a may be partially exposed or a gap may occur between the metal wire 208 and the electrode pad 205 in connecting the metal wire 208 to the pad 205.
In the case where the concave portion 207a is formed to penetrate through the electrode pad 205 into the interlayer insulating film 202, moisture penetrates within the interlayer insulating film 202 through the concave portion 207a of which the whole or a part is exposed, or through the gap between the metal wire 208 and the electrode pad 205.
Further, when the penetrated moisture reaches the ferroelectric capacitor 203, the possibility is increased that an abnormality occurs in the potential inversion of the capacitor 203, and as a result, the FeRAM element 200 is in danger of malfunctioning.
Herein, description is made by taking as an example a case of using the FeRAM element. Further, the problem caused by such penetration of moisture from the outside may similarly occur as long as the semiconductor device having an electrode pad is used. For example, there is a problem that migration of wiring materials easily occurs due to moisture which penetrates into the inside through an injured electrode pad.